1. Field of the Invention
The invention relates generally to pipeline connections, and more particularly to systems and methods for making connections between pipe sections where the connections form a conduit that is substantially free of gaps that can promote buildup of scale or solidified polymers that impede the flow of fluids through the pipeline, as well as crevice corrosion that can cause the connections to fail.
2. Related Art
The use of pipelines for handling fluids is widely known. High-volume pipelines are commonly used to carry oil, gas and other fluid hydrocarbons. High-pressure or high-temperature pipelines are commonly used in industrial applications. Pipelines may also be designed for many other purposes, such as carrying corrosive, toxic or otherwise dangerous fluids.
The pipelines used in these applications normally consist of a number of pipe sections which are connected end-to-end to form a single conduit. Typically, the pipe sections are joined by means of couplings or connectors which consist of a set of flanges attached to the ends of the pipe sections. The flanges are bolted or held together in some other manner to form a continuous conduit.
In order to ensure that the couplings between pipe sections form tight seals, conventional (e.g., ANSI) couplings normally include a gasket or some other type of seal ring positioned between the flanges of the couplings. As the flanges of the coupling are drawn together (e.g., by tightening a set of bolts that hold them together) the seal ring is compressed between the flanges. The coupling is tightened enough to apply a desired load between the flanges and the seal ring, thereby achieving the desired seal.
When a conventional coupling is fully assembled and tightened, there is normally a gap between the flanges. As noted above, the seal is provided by compression of the seal ring between the flanges, rather than contact between the flanges themselves. Further, it may be necessary to leave a gap between the flanges in order to account for manufacturing tolerances while still allowing the appropriate load to be applied to the seal ring. In some applications, however, the gap between the flanges may cause various problems.
In polymer processing systems, for example, the gap between the flanges can cause turbulence and/or stagnation in the flow of polymer materials which are transported through the pipelines. This, in turn, can cause the polymer materials to solidify and build up in the pipeline at the coupling. As the solidified polymer material builds up, the flow of the polymer material through the pipeline is restricted. The couplings in the pipeline must therefore be periodically dismantled and the solidified polymer material removed. This is an extremely expensive process, due to both the cost of dismantling/cleaning the couplings and the cost associated with downtime of the system.
In another example, the presence of a gap between the flanges can lead to crevice corrosion in pipelines that transport corrosive fluids. For instance, in one gasoline refining system, a hydrofluoric acid solution is transported through pipelines for use as a catalyst. The hydrofluoric acid solution is very reactive and therefore very corrosive. Gaps between the coupling flanges allow the hydrofluoric acid solution to react with the metal of the flanges, resulting in the build-up of scale and the leaching of carbon from the steel flanges. The scale can cause turbulence and hinder the flow of the acid solution through the pipeline, and the leaching of the carbon from the steel can make the steel more brittle and prone to failure.
It would therefore be desirable to provide systems and methods for connecting pipe sections for use in these types of industrial applications, where the couplings between pipe sections minimize or eliminate the gaps that are present between the flanges of conventional pipe couplings.